Re: Threading in new C++ standard

From:

Szabolcs Ferenczi <szabolcs.ferenczi@gmail.com>

Newsgroups:

comp.lang.c++,comp.soft-sys.ace

Date:

Thu, 17 Apr 2008 09:40:42 -0700 (PDT)

Message-ID:

<2427d471-dad0-4b26-ab9e-7eaf26353c9d@d1g2000hsg.googlegroups.com>

On Apr 16, 12:28 am, "Dann Corbit" <dcor...@connx.com> wrote:

Rather than create a new way of doing things:http://www.open-std.org/jtc1/=

sc22/wg21/docs/papers/2008/n2497.html

...

I like that some higher level construction is also there at last (at
condition_variable):

<quote>
template <class Predicate>
    void wait(unique_lock<mutex>& lock, Predicate pred);
Effects:
As if:
while (!pred())
    wait(lock);
</quote>

Now programming the get operation of a bounded buffer would look
something like this, I guess:

queue BB::q;
mutex BB::m;
condition_variable BB::empty;
condition_variable BB::full;
int BB::get()
{
   int b;
   unique_lock<mutex> lock(m);
   full.wait(lock, !q.empty());
   b = q.get();
   empty.notify_one();
   return b;
}

Although there is still some duplication in `full.wait(lock, !
q.empty());', it is much closer to this simple pseudo code (where
`when' is a keyword for a conditional critical region statement) than
a pthread version:

shared queue BB::q;
int BB::get()
{
   int b;
   when (!q.empty()) {
     b = q.get();
   }
   return b;
}

Best Regards,
Szabolcs